Chicken eggs are one of the most common allergy triggers in the world. Scientific tests have shown that 0.2% of the European population suffers from this allergy. The respondents themselves reported otherwise: 2.5% of the patients surveyed claimed to have an egg allergy (data from 2015).
The two main allergens are known as ovomucoid and ovalbumin. They are found in the egg white. Ovomucoid is acid resistant and heat stable. People who have an allergic reaction to ovomucoid usually cannot tolerate raw or cooked eggs. On the other hand, ovalbumin breaks down at high temperatures, so people who have an allergic reaction to ovalbumin can often tolerate cooked eggs. There are only a few reports of people with a chicken egg allergy who are also allergic to chicken meat. However, care must be taken with vaccines produced using a culture medium containing chicken egg. Eggs are also found in egg dishes and many processed foods that use eggs as a binder.
Symptoms occur within a short period of time following exposure, usually in the digestive tract. Allergic individuals may experience difficulty swallowing, nausea, vomiting, bloating and diarrhoea. The skin can also be affected, resulting in redness, hives and itching. Some patients also experience facial swelling. Egg allergies can also trigger atopic dermatitis or make it worse. As with other food allergies, respiratory symptoms can also occur, leading to allergic rhinitis or asthma symptoms. In rare cases, anaphylactic shock along with shortness of breath and cardiac arrest may occur.
Egg Allergy in Childhood
After milk allergies, egg allergies are the second most common allergic disease in childhood. They usually appear during the first two years of life. Children with egg allergies suffer from diarrhoea and vomiting, growth disorders and/or chronic skin inflammation (atopic eczema). In 50 – 80% of children with egg allergies, the allergy disappears spontaneously once they reach school age.
Egg Allergy in Adulthood
Egg allergies rarely appear in adulthood. Bird-egg syndrome, although rare, is worth noting. This occurs when bird keepers develop an allergy to bird droppings and feathers, leading to respiratory symptoms. Bird-egg syndrome can progress to an egg allergy. However, unlike primary allergies in childhood, the allergen implicated in bird-egg syndrome is found in the egg yolk rather than the egg white.
An important step in the diagnostic procedure is the patient history. The doctor asks the patient about his or her eating habits and symptoms and deduces the potential causes from this information. Depending on the symptoms, the suspected allergens are further investigated using a skin or blood test. These tests reveal an allergy susceptibility to a particular substance; however, they cannot provide evidence of any actual allergies. For this reason, the tests are followed by an additional diagnostic procedure called a provocation test. Patients are given a miniscule amount of an allergen under medical observation. In this way, it can be determined whether the egg triggers an allergy or if it can be eliminated from the list of suspected allergens.
The most important method for relieving symptoms is abstention, or allergen avoidance. It involves the elimination of eggs from the diet. This step should be taken under the supervision of a qualified nutritionist, and never without a medical diagnosis. If eggs can be tolerated at a later time, it is then no longer necessary to exclude them from the diet.
Drug therapies are indicated in people with very severe food allergies. Patients who experience severe reactions, such as anaphylactic shock, after exposure to the tiniest amounts of an allergen must always carry an emergency kit with them containing an adrenaline auto-injector, cortisone (in liquid or tablet form) and an antihistamine (in liquid or tablet form).
In terms of immunotherapy, which treats the causes of an allergy, there is no clear data available for egg allergies or food allergies in general. Recent studies from 2015 suggest that, in the case of peanut allergies, desensitisation may be possible. This involves giving the patient small amounts of the allergen and stimulating the immune system by building up to a larger amount of the trigger substance, which can then be tolerated by the end of the therapy. It is still unclear whether this therapy can be applied in the treatment of egg allergies in the future.
Prof. Dr. med. Dr. h.c. T. Zuberbier
Last changes made: July 2016